When producing consumer products out of different vegetable or animal oil deodorization is a part of the refining process. During the deodorization the oil is heated to a high temperature 180-275.degree. C. in order to remove contaminants and unwanted substances from the oil. These substances have a lower boiling point than the different triglycerides which constitute the fatty oil. The deodorization is carried through under vacuum 1-20 mbar and the removal is facilitated by adding stripping gas to the oil. The stripping gas may consist of an inert gas or steam. The stripping gas makes the mixing of the oil and the removal of the unwanted substances easier.
For many types of oils it is useful to heat the oil under vacuum with addition of stripping gas during a pretreatment step prior to the deodorization to remove the dissolved air and at that hinder oxidation of the oil.
The deodorized oil is also in many cases subjected to a further treatment with injection of stripping gas under vacuum during a simultaneous cooling.
The vacuum vessels which are used for preheating or cooling the oil which is to be deodorized have previously usually consisted of cylindrical pressure vessels with inserts provided with baffles. The baffles have been arranged such that the oil flows in a plug flow. In the vessels there are tubes for the heating/cooling medium and pipes for distribution of stripping gas. The cylindrical vessels have usually had double curved side walls which were welded to the cylindrical surface. The shape described above makes the application of the necessary couplings and connections for oil, heating/cooling medium, stripping gas and vacuum very costly and complicated. The cleaning of the vacuum vessels is also made more difficult.